JP4521257B2 - Heat treatment method and heat treatment apparatus - Google Patents

Description

  The present invention relates to a heat treatment method and a heat treatment apparatus for steel.

  Atmosphere control is important in heat treatment of steel materials, and such atmosphere control is performed by controlling the CP (carbon potential) of the heat treatment atmosphere.

  Conventionally, in carburizing heat treatment of steel materials, a method has been disclosed in which CP is stabilized at a constant value by controlling the supply amount of enriched gas (CmHn gas) based on CP (see, for example, Patent Document 1). Further, a method for stabilizing CP by feedback control such as proportional control and PID control is disclosed (for example, see Patent Document 2).

Japanese Patent Publication No. 5-15782 JP 2003-013136 A

  However, in the conventional heat treatment furnace, when the workpiece is loaded and unloaded, if the opening of the furnace is opened, air enters the furnace and CP is greatly reduced. There was a problem of overshoot. In addition, the control response may become unstable, causing hunting, and it may take some time to reach the target value.

  An object of the present invention is to provide a heat treatment method and a heat treatment apparatus capable of stably recovering CP to a target value even when CP is greatly reduced.

  In order to solve the above-mentioned problems, according to the present invention, there is provided a heat treatment method for supplying an enriched gas into a furnace and heat-treating an object to be treated in the furnace, wherein the enriched gas is based on a carbon potential in the furnace. By controlling the supply flow rate, the carbon potential is feedback-controlled, and when the furnace opening is open, and after the furnace opening is closed until the carbon potential in the furnace reaches the target value or for a predetermined time. Stops the feedback control, maintains the supply flow rate of the enriched gas immediately before stopping the feedback control, and when the carbon potential in the furnace reaches the target value after closing the furnace opening or when a predetermined time has elapsed, There is provided a heat treatment method characterized by performing the feedback control.

  The opening is a carry-in port for carrying the object to be processed into the furnace, and with the carry-in port of the furnace closed, the entrance of the carry-in chamber provided outside the carry-in port of the furnace is opened, It is good also as carrying in a to-be-processed object into a furnace by opening a carrying-in entrance of the said furnace after opening a to-be-processed body into a carrying-in chamber and closing the entrance of the said carrying-in chamber.

  The opening is a carry-out port for carrying out the object to be processed out of the furnace, and with the oil tank chamber outlet provided outside the furnace carry-out port closed, the carry-out port of the furnace is opened, It is good also as carrying out a to-be-processed object from the said oil tank chamber by opening the exit of the said oil tank chamber after opening a process body in the said oil tank chamber and closing the carrying-out port of the said furnace.

  The feedback control may be PID control. Further, the maximum supply flow rate of the enriched gas may be increased as the surface area of the object to be processed existing in the furnace increases.

  According to the present invention, there is also provided a heat treatment apparatus for supplying an enriched gas into a furnace and heat-treating an object to be treated in the furnace, wherein the enriched gas is provided in the enriched gas supply path based on a carbon potential in the furnace. And a feedback control system for feedback control of the carbon potential is configured, and the regulator controls the opening of the furnace and the opening of the furnace. The adjustment of the regulator is stopped until the carbon potential in the furnace reaches the target value after the closing or for a predetermined time, and the carbon potential in the furnace reaches the target value after the furnace opening is closed or the predetermined value. When the time has elapsed, the controller is adjusted, and the flow control valve is in a state immediately before the controller is stopped while the controller is stopped. It takes and maintains the opening degree, the heat treatment apparatus is provided.

  The opening is a carry-in port for carrying the workpiece into the furnace, and a carry-in chamber may be provided outside the carry-in port of the furnace. The opening is a carry-out port for carrying out the object to be processed out of the furnace, and an oil tank chamber may be provided outside the carry-out port of the furnace. The feedback control may be PID control.

  According to the present invention, when the furnace opening is opened, the feedback control is stopped and the supply flow rate of the enriched gas is made constant to prevent the CP from becoming unstable. Can be quickly recovered. CP can be easily stabilized without complicated control settings. The carburization depth can be made appropriate by changing the maximum supply flow rate of the rich gas in accordance with the surface area of the object to be processed existing in the furnace.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, a carburizing apparatus 1 as a heat treating apparatus for carrying out a carburizing process method as a heat treatment method according to the present invention includes a heat treatment furnace 3 for performing a heat treatment of an object 2 to be treated. . A carry-in chamber 5 is provided in front of the heat treatment furnace 3 (left side in FIG. 1). An oil tank chamber 6 is provided behind the heat treatment furnace 3 (right side in FIG. 1). In the heat treatment furnace 3, a preheating chamber 11, a carburizing chamber 12, a diffusion chamber 13, a descending chamber 14, and a soaking chamber 15 are provided in this order toward the rear. The atmospheres in the preheating chamber 11, the carburizing chamber 12, the diffusion chamber 13, the descending room 14, and the soaking chamber 15 are in communication with each other.

  In the carry-in chamber 5, an inlet 21 for carrying the workpiece 2 into the carry-in chamber 5 is formed, and a door 22 for opening and closing the inlet 21 is provided. An excess 23 is provided in the upper part of the carry-in chamber 5.

  At the front part of the heat treatment furnace 3, a carry-in entrance 31 is formed as an opening for carrying the workpiece 2 from the carry-in chamber 5 into the heat treatment furnace 3, and a door 32 for opening and closing the carry-in entrance 31 is provided. The carry-in chamber 5 described above is provided outside the carry-in port 31 and communicates with the heat treatment furnace 3 through the carry-in port 31. The door 32 is provided with a hole 32a. At the rear part of the heat treatment furnace 3, a carry-out port 33 is formed as an opening for carrying out the object 2 from the heat treatment furnace 3 and carrying it into the oil tank chamber 6, and a door 34 for opening and closing the carry-out port 33 is provided. Yes. The oil tank chamber 6 described above is provided outside the carry-out port 33 and communicates with the heat treatment furnace 3 through the carry-out port 33. The door 34 is provided with a hole 34a.

  A roller conveyor 35 that conveys the workpiece 2 from the carry-in port 31 toward the carry-out port 33 is provided in the lower part of the heat treatment furnace 3. The workpiece 2 is transported by the roller conveyor 35 so as to pass through the preheating chamber 11, the carburizing chamber 12, the diffusion chamber 13, the cooling chamber 14, and the soaking chamber 15 in this order.

Further, the heat treatment furnace 3 includes an enrich gas supply circuit 41 that supplies, for example, city gas as an enrich gas, an RX gas (CO gas) supply circuit 42, an air supply circuit 43 that supplies air, and nitrogen (N ₂ ). A gas supply circuit 44 is connected.

  The enrich gas supply circuit 41 includes a supply path 52 for supplying the enrich gas to the carburizing chamber 12, a supply path 53 for supplying the enrich gas to the diffusion chamber 13, and a supply path 55 for supplying the enrich gas to the soaking chamber 15. ing. Flow rate adjustment valves 62, 63, and 65 are interposed in the supply paths 52, 53, and 55, respectively. The flow rate adjusting valves 62, 63, 65 are adjusted in opening degree by the output signal of the adjuster 68.

  The RX gas supply circuit 42 includes a supply path 71 that supplies RX gas to the preheating chamber 11, a supply path 72 that supplies RX gas to the carburizing chamber 12, a supply path 73 that supplies RX gas to the diffusion chamber 13, and a soaking A supply path 75 for supplying RX gas to the chamber 15 is provided. The air supply circuit 43 includes a supply path 81 that supplies air to the preheating chamber 11, a supply path 82 that supplies air to the carburizing chamber 12, and a supply path 84 that supplies air to the greenhouse 14. The nitrogen gas supply circuit 44 includes a supply path 91 for supplying nitrogen gas to the preheating chamber 11, a supply path 92 for supplying nitrogen gas to the carburizing chamber 12, and a supply path 94 for supplying nitrogen gas to the descending chamber 14. Yes.

Above the preheating chamber 11, the carburizing chamber 12, the diffusion chamber 13, the descending chamber 14, and the soaking chamber 15, fans 100 for stirring the furnace atmosphere are provided. Although not shown, heaters are provided on both sides of the roller conveyor 35 in the preheating chamber 11, the carburizing chamber 12, the diffusion chamber 13, the descending chamber 14, and the soaking chamber 15. The carburizing chamber 12, the diffusion chamber 13, and the soaking chamber 15 are provided with oxygen (O ₂ ) sensors 101, 102, and 103, respectively. The detection values of the oxygen sensors 101, 102, 103 are transmitted to the controller 68.

  The controller 68 has a function of calculating each CP in the carburizing chamber 12, the diffusion chamber 13, and the soaking chamber 15 based on the detection values of the oxygen sensors 101, 102, 103, and the carburizing chamber 12, the diffusion chamber. 13. It has a function of a PID (proportional / integral / derivative) controller that adjusts the opening degree of each of the flow rate adjusting valves 62, 63, 65 based on each CP in the soaking chamber 15. That is, the controller 68 compares each CP in the carburizing chamber 12, the diffusion chamber 13, and the soaking chamber 15 obtained by calculation with each target value, and adjusts the flow rate adjusting valve so that each CP becomes a target value. The operation amounts 62, 63, 65 are obtained, and operation signals are transmitted to the flow rate adjusting valves 62, 63, 65. Then, the opening degree of the flow rate adjusting valves 62, 63, 65 is adjusted in accordance with the operation signal of the adjuster 68, whereby the rich gas supply flow rates from the supply paths 52, 53, 55 are adjusted. That is, a PID control system 105 as a feedback control system including the oxygen sensor 101, the regulator 68 and the flow rate adjustment valve 62, and a PID control as a feedback control system including the oxygen sensor 102, the regulator 68 and the flow rate adjustment valve 63. A system 106 and a PID control system 107 as a feedback control system including an oxygen sensor 103, a regulator 68, and a flow rate adjustment valve 65 are configured, and the CP in the carburizing chamber 12 is controlled by the PID control system 105 and diffused. The CP in the chamber 13 is controlled by the PID control system 106, and the CP in the soaking chamber 15 is controlled by the PID control system 107.

  An oil tank 115 is provided below the oil tank chamber 6. Further, an outlet 116 for carrying out the workpiece 2 from the oil tank chamber 6 is formed, and a door 117 for opening and closing the outlet 116 is provided. An excision 118 is provided in the upper part of the oil tank chamber 6.

  The atmosphere in the heat treatment furnace 3 flows into the carry-in chamber 5 and the oil tank chamber 6 through the hole 32a of the door 32 and the hole 34a of the door 34, and is exhausted from the exhausts 23 and 118. The furnace pressure in the heat treatment furnace 3 is controlled by controlling the openings of the executions 23 and 118.

  In addition, the carburizing apparatus 1 is provided with a sequencer 120 that controls processes in the carburizing apparatus 1. The controller 68 described above is connected to the sequencer 120 via a network or the like. The sequencer 120 can transmit an instruction to stop or restart the PID adjustment to the adjuster 68 according to the state of the carburizing apparatus 1. For example, when the carry-in port 31 and the carry-out port 33 of the heat treatment furnace 3 are opened, the sequencer 120 gives a command for stopping the PID adjustment to the adjuster 68. Thereby, each PID control of the PID control systems 105, 106, and 107 is stopped.

  FIG. 2 shows changes in pressure in the heat treatment furnace 3 when the inlet 31 and the outlet 33 are opened with the inlet 21 of the inlet chamber 5 and the outlet 116 of the oil tank chamber 6 closed. 3 and 4 show the change in the CP in the carburizing chamber 12 and the change in the supply flow rate of the rich gas from the supply path 52, respectively. When the inlet 21 or the outlet 33 of the heat treatment furnace 3 starts to open with the inlet 21 of the inlet chamber 5 and the outlet 116 of the oil tank chamber 6 closed (S1 in FIG. 2), the inside of the inlet chamber 5 or the oil tank chamber 6 The low temperature atmosphere is heated by the radiant heat from the heat treatment furnace 3 and rapidly expands, and the pressure in the heat treatment furnace 3 rises as shown in FIG. After that, when the carry-in port 31 or the carry-out port 33 starts to close (S2 in FIG. 2), the pressure in the heat treatment furnace 3 rapidly decreases. When the carry-in port 31 or the carry-out port 33 is closed (S3 in FIG. 2), after the pressure in the heat treatment furnace 3 continues to drop, air is sucked from the outside of the heat treatment furnace 3. Therefore, as shown in FIG. 3, the CP in the carburizing chamber 12 is rapidly lowered. Thus, when the PID control of the PID control system 105 is continued as it is when the CP sharply decreases, the supply flow rate of the enriched gas from the supply path 52 is rapidly increased as shown by the one-dot chain line in FIG. The CP of the carburizing chamber 12 overshoots as indicated by the alternate long and short dash line in FIG. Then, problems such as CP becoming unstable and hunting occurs, or it takes time to reach the target value, and control is not performed satisfactorily. On the other hand, if the PID control of the PID control system 105 is stopped when the CP of the carburizing chamber 12 rapidly decreases, the CP does not change in an unstable manner. As shown by the solid line in FIG. 4, when the enrich gas supply flow rate is maintained at a constant value, the CP gradually increases and approaches the target value of CP, as shown by the solid line in FIG. Then, if the PID control of the PID control system 105 is resumed after the CP of the carburizing chamber 12 has almost reached the target value, there is no possibility that the CP will become unstable. In addition, the CP can be quickly recovered to the target value as compared with the case where the PID control is continued. For the above reasons, the sequencer 120 gives a command for opening the carry-in port 31 and the carry-out port 33 of the heat treatment furnace 3 and at the same time gives a command for stopping the PID adjustment to the adjuster 68, so that the PID control system 105 The PID control is stopped to prevent the CP of the carburizing chamber 12 from changing in an unstable manner. Similarly, when opening the carry-in port 31 and the carry-out port 33, the PID control of the PID control systems 106 and 107 is stopped, and each CP of the diffusion chamber 13 and the soaking chamber 15 is prevented from changing unstablely. The target value can be recovered quickly.

  When the controller 68 stops the PID adjustment according to a command from the sequencer 120, the flow rate adjustment valves 62, 63, 65 maintain the opening degree of the flow rate adjustment valves 62, 63, 65 just before the PID adjustment is stopped. It has become so. That is, the rich gas supply flow rates from the supply paths 52, 53, and 55 are respectively maintained at values immediately before the PID control by the PID control systems 105, 106, and 107 is stopped.

  The controller 68 stops the PID adjustment in accordance with a command from the sequencer 120, and then performs the PID adjustment after a while has passed since the loading / unloading port 31 or the loading / unloading port 33 is opened / closed. That is, the adjuster 68 sets each CP of the carburizing chamber 12, the diffusion chamber 13, and the soaking chamber 15 when the carry-in port 31 and the carry-out port 33 are opened and after the carry-in port 31 and the carry-out port 33 are closed. PID adjustment is stopped until it reaches the value, or when the CPs of the carburizing chamber 12, the diffusion chamber 13, and the soaking chamber 15 reach the target values after closing the carry-in port 31 and the carry-out port 33, PID adjustment is resumed. Thereby, when PID adjustment is restarted, each CP can be stably controlled. The timing at which the PID adjustment is resumed is, for example, an average until the respective CPs of the carburizing chamber 12, the diffusion chamber 13, and the soaking chamber 15 approach each target value after the carry-in port 31 and the carry-out port 33 are closed. For example, a specific time may be set as a predetermined time, and may be set beforehand so that PID adjustment is started when each CP of the carburizing chamber 12, the diffusion chamber 13, and the soaking chamber 15 recovers. For example, the controller 68 may be set so that the PID adjustment is automatically restarted after a predetermined time has elapsed since the PID adjustment was stopped. When the carry-in port 31 and the carry-out port 33 are closed, a signal for resuming PID adjustment is transmitted from the sequencer 120 to the adjuster 68, and when a predetermined time has elapsed after receiving the signal, the adjuster 68. May be set to automatically resume PID adjustment. The predetermined time is not limited to the average time until the CP approaches the target value. The target value of each CP may be the CP target value itself, but may be a value close to the CP target value. For example, specifically, a value of about ± 0.25%, a value of about ± 0.1%, a value of about ± 0.05%, etc. from the target value of CP. The timing for resuming the PID control may be determined by setting a predetermined time in advance as described above. However, for example, the measured value of each CP detected by the controller 68 is a target value or a target value. It may be set so that the controller 68 automatically resumes PID adjustment when a value close to the value is reached.

  Next, the carburizing process of the to-be-processed object 2 using the carburizing apparatus 1 comprised as mentioned above is demonstrated.

  First, in the carburizing apparatus 1 before carrying in the to-be-processed object 2 which has not yet been processed, the several to-be-processed objects 2 carried in the heat treatment furnace 3 previously are processed. The composition, temperature, pressure, and the like of the furnace atmosphere in the preheating chamber 11, the carburizing chamber 12, the diffusion chamber 13, the descending chamber 14, and the soaking chamber 15 are adjusted to desired values, respectively. RX gas is supplied from supply paths 72, 73, and 75 of the RX gas supply circuit 42 at a constant supply flow rate. The enriched gas is supplied into the heat treatment furnace 3 from the supply paths 52, 53, and 55 of the enriched gas supply circuit 41 while the supply flow rate is adjusted by the PID control systems 105, 106, and 107. The controller 68 calculates the CPs of the carburizing chamber 12, the diffusion chamber 13, and the soaking chamber 15 based on the detection values of the oxygen sensors 101, 102, and 103, and sets the respective opening amounts of the flow control valves 62, 63, and 65. It is operating. By adjusting the rich gas supply flow rate in this way, the CPs of the carburizing chamber 12, the diffusion chamber 13, and the soaking chamber 15 are maintained at substantially predetermined target values. In addition, the target value of CP of the carburizing chamber 12 is about 1.0%, for example, and the target value of CP of the diffusion chamber 13 is about 0.8%, for example, and the target value of CP of the soaking chamber 15 is about The value is about 1.0%, for example. The atmosphere in the heat treatment furnace 3 flows into the carry-in chamber 5 and the oil tank chamber 6 through the hole 32 a of the door 32 and the hole 34 a of the door 34, and is exhausted from the exhausts 23 and 118. For example, the furnace pressure is adjusted to about 8 mmAq. Further, the atmosphere in the heat treatment furnace 3 is heated by a heater (not shown). For example, the temperature of the preheating chamber 11 is about 930 ° C., the temperature of the carburizing chamber 12 is about 930 ° C. to 950 ° C. The temperature is adjusted to about 930 ° C. to 950 ° C., the temperature of the descending chamber 14 is adjusted to about 930 ° C. to 850 ° C., and the temperature of the soaking chamber 15 is adjusted to about 850 ° C.

  Thus, in the state where the atmosphere in the heat treatment furnace 3 is adjusted, the inlet 21 of the carry-in chamber 5 is opened, and the workpiece 2 is carried into the carry-in chamber 5. When the entrance 21 of the carry-in chamber 5 is opened, the carry-in port 31 of the heat treatment furnace 3 is kept closed. When the workpiece 2 is loaded into the loading chamber 5, the inlet 21 of the loading chamber 5 is closed.

  Next, the inlet 31 of the heat treatment furnace 3 is opened to move the workpiece 2 from the carry-in chamber 5 into the heat treatment furnace 3, and at the same time, the outlet 33 is opened to finish the treatment in the soaking chamber 15. The body 2 is moved from the heat treatment furnace 3 to the oil tank chamber 6, but immediately before starting to open the carry-in port 31 and the carry-out port 33, a command to stop the PID adjustment is transmitted from the sequencer 120 to the adjuster 68. As a result, the controller 68 stops the PID adjustment, and the PID control of the PID control systems 105, 106, 107 is stopped. When the controller 68 stops the PID adjustment, the flow rate adjusting valves 62, 63, 65 maintain the opening degree immediately before stopping the PID adjustment. That is, the enrich gas supply flow rates from the supply paths 52, 53, and 55 of the enrich gas supply circuit 41 are respectively maintained at constant values immediately before the PID adjustment is stopped.

  When the doors 32 and 34 start to rise and the carry-in port 31 and the carry-out port 33 begin to open (S1 in FIG. 2), the atmosphere in the carry-in chamber 5 and the atmosphere in the oil tank chamber 6 are caused by the radiant heat from the heat treatment furnace 3. The temperature is raised. When the carry-in port 31 and the carry-out port 33 are opened, the inlet 21 of the carry-in chamber 5 and the outlet 116 of the oil tank chamber 6 are closed, and the atmosphere in the carry-in chamber 5 and the atmosphere in the oil tank chamber 6 rapidly expand. The atmosphere in the heat treatment furnace 3 is pressurized.

  When the carry-in port 31 and the carry-out port 33 of the heat treatment furnace 3 are opened, the workpiece 2 is carried into the heat treatment furnace 3 from the carry-in chamber 5 through the carry-in port 31 and the treatment in the soaking chamber 15 is completed. The processing body 2 is unloaded from the heat treatment furnace 3 to the oil tank chamber 6 through the unloading port 33. Thereafter, the doors 32 and 34 are lowered to close the carry-in port 31 and the carry-out port 33. When the doors 32 and 34 begin to be lowered and the carry-in port 31 or the carry-out port 33 begins to close (S2 in FIG. 2), the pressure in the heat treatment furnace 3 drops rapidly. The carry-in port 31 or the carry-out port 33 is closed (S3 in FIG. 2), and the pressure in the heat treatment furnace 3 continues to decrease thereafter. The pressure is lower than the pressure before opening the carry-in port 31 and the carry-out port 33, and becomes a negative pressure from the outside of the heat treatment furnace 3. Then, air begins to be sucked into the heat treatment furnace 3 from the outside through the hole 32a of the door 32, the hole 34a of the door 34, and the like, and the pressure in the heat treatment furnace 3 starts to rise. As air enters the heat treatment furnace 3, the CP in the carburizing chamber 12 is significantly lowered from the target value as shown in FIG. 3. Similarly, the CPs of the diffusion chamber 13 and the soaking chamber 15 also drop significantly with respect to their target values. Thus, while the CP in the heat treatment furnace 3 decreases, the PID control by the PID control system 105 is stopped, and the enriched gas is supplied from the supply path 52 at a constant flow rate as shown in FIG. . When the pressure in the heat treatment furnace 3 recovers and air is not sucked, the CP of the carburizing chamber 12 stably approaches the target value without overshooting, as shown by the solid line in FIG. Similarly, while the CP in the heat treatment furnace 3 decreases, the PID control by the PID control systems 106 and 107 is stopped, and the enriched gas is supplied from the supply paths 53 and 55 at a constant flow rate, so that the diffusion chamber 13 Each CP of the soaking chamber 15 approaches the target value stably. In this case, compared with the case where the PID control of the PID control systems 105, 106, 107 is continued, each CP of the carburizing chamber 12, the diffusion chamber 13, and the soaking chamber 15 can be quickly recovered to the target value. Further, there is no possibility that hunting occurs due to instability of each CP, and each CP can be recovered in a stable state.

  The controller 68 starts the PID adjustment again after a while after the PID adjustment is stopped. When the controller 68 starts PID adjustment, each CP calculated based on the detected values of the oxygen sensors 101, 102, 103 is almost the target value, so that the PID control systems 105, 106, There is no possibility that the control response by 107 becomes unstable or hunting occurs, and the CPs of the carburizing chamber 12, the diffusion chamber 13, and the soaking chamber 15 can be stabilized at their respective target values.

  In this way, the object to be processed 2 is sequentially processed while adjusting the pressure in the heat treatment furnace 3, the CP, and the like. The object to be processed 2 carried into the heat treatment furnace 3 is placed on a roller conveyor 35, and sequentially passes through the preheating chamber 11, the carburizing chamber 12, the diffusion chamber 13, the cooling chamber 14, and the soaking chamber 15 by driving the roller conveyor 35. Preheating, carburizing, diffusion, cooling, and soaking are sequentially performed.

  It should be noted that the workpiece 2 is moved from the preheating chamber 11 to the carburizing chamber 12, moved from the carburizing chamber 12 to the diffusion chamber 13, moved from the diffusion chamber 13 to the descending chamber 14, and leveled from the descending chamber 14. When moving to the heat chamber 15, the carry-in port 31 and the carry-out port 33 of the heat treatment furnace 3 are opened each time, and a new workpiece 2 is carried from the carry-in chamber 5 into the preheating chamber 11 and at the same time the soaking chamber 15. The to-be-processed object 2 which completed the process in is carried out to the oil tank chamber 6, and the carrying-in port 31 and the carrying-out port 33 are closed. In this way, the workpiece 2 is continuously supplied to the preheating chamber 11, the carburizing chamber 12, the diffusion chamber 13, the descending chamber 14, and the soaking chamber 15, and is continuously processed. Also in these cases, immediately before opening the carry-in port 31 and the carry-out port 33, a command for stopping PID adjustment is transmitted from the sequencer 120 to the controller 68 each time, and each PID of the PID control systems 105, 106, 107 is sent. Control can be paused. Then, the enriched gas is supplied from the supply paths 52, 53, 55 at a constant flow rate, and when the CP in the heat treatment furnace 3 reaches the target value or when a predetermined time elapses, the PID by the PID control systems 105, 106, 107 is obtained. Control begins again. Therefore, since CP can be recovered quickly in a stable state, each treatment in the preheating chamber 11, the carburizing chamber 12, the diffusion chamber 13, the descending chamber 14, and the soaking chamber 15 is performed satisfactorily.

  When the soaking process in the soaking chamber 15 is completed, the unloading port 33 of the heat treatment furnace 3 is opened and the workpiece 2 is moved from the heat treatment furnace 3 to the oil tank chamber 6. As described above, when the carry-out port 33 is opened, the outlet 116 of the oil tank chamber 6 is closed. When the workpiece 2 is carried into the oil tank chamber 6 from the heat treatment furnace 3, the carry-out port 33 is closed. Then, in the oil tank chamber 6, the oil tank 115 is immersed and oil-quenched, pulled up from the oil tank 115, and then opened and discharged. When the outlet 116 is opened, the carry-out port 33 of the heat treatment furnace 3 is kept closed. As described above, a series of processes in the carburizing apparatus 1 is completed.

  According to the carburizing treatment method and the carburizing treatment apparatus 1, when the carry-in port 31 or the carry-out port 33 of the heat treatment furnace 3 is opened and after the carry-in port 31 or the carry-out port 33 of the heat treatment furnace 3 is closed, the heat treatment furnace 3. Until each of the CPs reaches the target value or for a predetermined time, each PID control by the PID control systems 105, 106, 107 is stopped, and the enrichment from the supply paths 52, 53, 55 immediately before each PID control is stopped. By maintaining the gas supply flow rate, the CP in the heat treatment furnace 3 does not change in an unstable manner, and the CP can be quickly recovered to the target value. When the CP in the heat treatment furnace 3 reaches the target value after the carry-in port 31 or the carry-out port 33 is closed or when a predetermined time has elapsed, each PID control by the PID control systems 105, 106, 107 is performed. , CP can be controlled in a stable state. Therefore, the process of the to-be-processed object 2 in the heat processing furnace 3 is performed favorably, and the reliability of the process can be improved. CP control can be easily stabilized without complicated control settings.

  Although an example of a preferred embodiment of the present invention has been described above, the present invention is not limited to the embodiment described here. For example, in this embodiment, the PID control is performed by the PID control systems 105, 106, and 107, but the CP may be controlled by other feedback control. For example, the controller 68 has a function of a PI (proportional / integral) controller, and each CP in the carburizing chamber 12, the diffusion chamber 13, and the soaking chamber 15 includes the oxygen sensor 101, 102 or 103, the controller 68, It is good also as controlling by the PI control system as a feedback control system comprised by the flow regulating valve 62, 63, or 65, respectively.

  The maximum supply flow rate of the enriched gas is normally set based on the state in which the maximum number of objects 2 that can be accommodated in the heat treatment furnace 3 exists. When the total surface area of the objects to be processed 2 is small, such as when the number of objects to be processed 2 is small, there is a problem that carbon is excessively supplied and the carburization depth becomes too deep. Further, in the present embodiment, the CP is obtained based on the detection values of the oxygen sensors 101, 102, 103. In this case, however, if the supply flow rate of the enrich gas is larger than the amount of carbon to be carburized. There is a problem in that the reliability of the CP calculated based on the detection values of the oxygen sensors 101, 102, 103 is lowered. Therefore, as shown in FIG. 5, the maximum supply flow rate of the enriched gas may be increased as the total surface area of the workpiece 2 existing in the heat treatment furnace 3 is increased. In this case, when the surface area of the workpiece 2 is small, the carburization depth can be prevented from becoming too deep. Further, since the reliability of the CP based on the detection values of the oxygen sensors 101, 102, 103 can be improved, the CP can be reliably controlled. In addition, the consumption of enriched gas can be reduced, and costs can be saved.

  In the example shown in FIG. 5, when there is only one target object 2 in the heat treatment furnace 3, the maximum supply flow rate of the rich gas from the supply paths 52, 53, and 55 is set to 1 L / min, respectively. When the maximum supply flow rate of the enriched gas is increased in proportion to the number of the objects to be processed 2 present in the interior, and there are 13 objects to be processed 2 in the heat treatment furnace 3, that is, in the heat treatment furnace 3. When there are the maximum number of objects 2 that can be stored, the maximum supply flow rate of the enriched gas from the supply paths 52, 53, and 55 is set to 4 L / min. The supply flow rate of the enrich gas is proportional to the opening degree of the flow rate adjustment valves 62, 63, 65. When the opening degree of the flow rate adjustment valves 62, 63, 65 is 100%, the supply flow rate of the enrich gas is 4L / For example, when the opening degree of the flow rate adjusting valves 62, 63, 65 is 25%, the enrich gas supply flow rate is 25% (1 L / min).

  In addition, the sequencer 120 grasps the number of the objects to be processed 2 existing in the heat treatment furnace 3 from the number of the objects to be processed 2 carried into and out of the heat treatment furnace 3, and according to the number, It has a function of setting an output limit for the output signal of the regulator 68 for adjusting the opening degree of the flow rate regulating valves 62, 63, 65. The output limit is transmitted from the sequencer 120 to the controller 68.

  When the output limit of the regulator 68 is not set, the opening degree of the flow rate regulating valves 62, 63, 65 increases in proportion to the output from the regulator 68, and the output of the regulator 68 is 100%. , The opening degree of the flow regulating valves 62, 63, 65 is set to be 100%. When the output limit of the regulator 68 is set to 50%, for example, when the output calculated by the regulator 68 is 50% or less, the output as calculated is transmitted. When the output exceeds 50%, 50% output is transmitted. Therefore, the opening degree of the flow rate adjusting valves 62, 63, 65 is suppressed to a range of 50% or less. Similarly, when the output limit of the regulator 68 is set to, for example, 25%, the output of the regulator 68 is set to 25% or less, and the opening degree of the flow rate adjusting valves 62, 63, 65 is set to 25% or less. It has come to be.

  In such a configuration, for example, immediately after the operation of the carburizing apparatus 1 is started, when the workpiece 2 has not yet been loaded, the sequencer 120 instructs the controller 68 to set the output limit to 25%. Is transmitted so that the opening degree of the flow rate adjusting valves 62, 63, 65 does not rise above 25%. That is, the maximum supply flow rate of the enrich gas is set to about 1 L / min. In this state, PID control is performed by the PID control systems 105, 106, and 107, and CPs are set to target values (for example, about 1.0%, 0.8%, 1 in the carburizing chamber 12, the diffusion chamber 13, and the soaking chamber 15, respectively). The pressure in the heat treatment chamber 3 is adjusted to about 8 mmAq, for example.

  In this way, the first object to be processed 2 is carried into the heat treatment furnace 3 whose atmosphere is adjusted, and the processing is started. Next, when the second object to be processed 2 is carried into the heat treatment furnace 3, the output limit is increased and the maximum supply flow rate of the enriched gas is increased. In this state, PID control is performed by the PID control systems 105, 106, and 107, and CPs are set to target values (for example, about 1.0%, 0.8%, 1 in the carburizing chamber 12, the diffusion chamber 13, and the soaking chamber 15, respectively). (About 0.0%). The pressure in the heat treatment chamber 3 is maintained at, for example, about 8 mmAq by adjusting the displacement. Thus, when there are two workpieces 2 in the heat treatment furnace 3, the amount of carbon that can be supplied can be increased by increasing the maximum supply flow rate of the enrich gas. Therefore, each workpiece 2 can be sufficiently carburized.

  Thus, every time the number of objects to be processed 2 carried into the heat treatment furnace 3 increases, the output limit of the regulator 68 is increased to increase the maximum supply flow rate of the enriched gas. When the number of objects to be processed 2 in the heat treatment furnace 3 reaches the maximum (13), the output limit of the adjuster 68 is released. Further, when the carrying-in of a new object to be processed 2 is stopped and the number of objects to be processed 2 decreases from the heat treatment furnace 3, for example, when the operation of the carburizing apparatus 1 is ended, The maximum supply flow of enriched gas is reduced according to the number. As described above, the maximum supply flow rate of the enriched gas is changed according to the number of the objects to be processed 2 existing in the heat treatment furnace 3, that is, the surface area of the objects to be processed 2 existing in the heat treatment furnace 3. Since the amount of carbon inside can be adjusted to not too much, the carburization depth can be made appropriate. In addition, the reliability of the CP based on the detection values of the oxygen sensors 101, 102, and 103 and the reliability of the control of the CP can be improved.

  In the above embodiment, the maximum supply flow rate of the enriched gas is increased according to the number of the objects to be processed 2 in the heat treatment furnace 3, but for example, the larger the size of the object to be processed 2, that is, The maximum supply flow rate of the enriched gas may be increased according to the surface area of the workpiece 2 existing in the heat treatment furnace 3.

It is a schematic sectional drawing explaining the structure of a carburizing processing apparatus. It is a graph explaining the change of the pressure in a heat processing furnace. It is a graph explaining the change of CP in a carburizing furnace. It is a graph explaining the change of the supply flow rate of the rich gas to a carburizing furnace. In another embodiment, it is a graph explaining the relationship between the number of to-be-processed objects, and the maximum supply flow volume of rich gas.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Carburizing process apparatus 2 To-be-processed object 3 Heat treatment furnace 5 Carrying-in room 6 Oil tank room 21 Inlet of carrying-in room 31 Carry-in inlet of heat-treating furnace 33 Outlet of heat-treating furnace 68 Controller 105,106,107 PID control system 116 Outlet of oil-tank room

Claims (9)

A heat treatment method of supplying an enriched gas into a furnace and heat-treating an object to be treated in the furnace,
By controlling the supply flow of the enriched gas based on the carbon potential in the furnace, the carbon potential is feedback controlled,
When the furnace opening is open and until the carbon potential in the furnace reaches the target value after closing the furnace opening or for a predetermined time, immediately before stopping the feedback control. Maintain the supply flow of enriched gas at
A heat treatment method, wherein the feedback control is performed when the carbon potential in the furnace reaches a target value after a furnace opening is closed or when a predetermined time elapses. The opening is a carry-in port for carrying the workpiece into the furnace,
With the furnace entrance closed, the entrance of the carry-in chamber provided outside the furnace entrance is opened, and the object to be processed is carried into the carry-in chamber.
2. The heat treatment method according to claim 1, wherein after the entrance of the carry-in chamber is closed, the carry-in entrance of the furnace is opened and the object to be treated is carried into the furnace. The opening is a carry-out port for carrying out the workpiece from the furnace,
With the outlet of the oil tank chamber provided outside the furnace outlet being closed, the furnace outlet is opened, and the object to be processed is carried into the oil tank chamber,
3. The heat treatment method according to claim 1, wherein after closing the outlet of the furnace, the outlet of the oil tank chamber is opened and the object to be processed is carried out of the oil tank chamber. The heat treatment method according to claim 1, wherein the feedback control is PID control. 5. The heat treatment method according to claim 1, wherein the maximum supply flow rate of the enriched gas is increased as the surface area of the object to be processed existing in the furnace increases. A heat treatment apparatus for supplying an enriched gas into a furnace and heat-treating an object to be treated in the furnace,
A controller for adjusting the opening of a flow rate adjustment valve provided in the supply path of the enriched gas based on the carbon potential in the furnace, and a feedback control system for feedback control of the carbon potential is configured;
The regulator stops the regulation of the regulator when the furnace opening is open and until the carbon potential in the furnace reaches a target value or after a predetermined time after the furnace opening is closed, When the carbon potential in the furnace reaches the target value after closing the furnace opening or when a predetermined time has elapsed, the controller is adjusted,
The flow rate adjusting valve maintains an opening degree immediately before stopping the adjustment of the regulator while the adjustment of the regulator is stopped. The opening is a carry-in port for carrying the workpiece into the furnace,
The heat treatment apparatus according to claim 6, wherein a carry-in chamber is provided outside the carry-in port of the furnace. The opening is a carry-out port for carrying out the workpiece from the furnace,
The heat treatment apparatus according to claim 6 or 7, wherein an oil tank chamber is provided outside the carry-out port of the furnace. The heat treatment apparatus according to claim 6, wherein the feedback control is PID control.

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